Thin film resistor technology is widely used in the semiconductor manufacturing industry. The prior art methods that are currently available for patterning thin film resistors suffer from the effects of topography on the critical dimensions (CDs) of the thin film resistor. In addition, some prior art methods for patterning thin film resistors create metal “stringers” that are capable of electrically shorting the thin film resistors. For example, consider the structure of the prior art thin film resistor shown below in FIGS. 1-6.
FIG. 1 illustrates a cross sectional view of a prior art semiconductor device 100 comprising a thin film resistor (TFR) 120. To create semiconductor device 100 a substrate of dielectric material 110 was provided as shown in FIG. 1. A layer of thin film resistor (TFR) material 120 was deposited on the dielectric material 110 and then masked (photolithography) and etched. A layer of thin film resistor (TFR) protection material 130 (e.g., titanium tungsten) was deposited over the thin film resistor (TRF) 120. The layer of TFR protection material 130 (and portions of the dielectric substrate 110) were then etched and a first titanium/titanium nitride (Ti/TiN) liner 140 was deposited. Then a layer of tungsten (W) 150 was deposited to cover the first titanium/titanium nitride (Ti/TiN) liner 140.
Then a tungsten etch back process is applied to etch away the tungsten layer 150 down to the first titanium/titanium nitride (Ti/TiN) liner 140. The result of applying the tungsten etch back process is shown in FIG. 2. Spacers (also known as “stringers”) of tungsten material 150 remain adjacent to the vertical edges of the portion of the first titanium/titanium nitride (Ti/TiN) liner 140 that is located over the TFR protection material 130 over the thin film resistor 120.
Then a second titanium/titanium nitride (Ti/TiN) liner 310 is deposited over the first titanium titanium/titanium nitride (Ti/TiN) liner 140 and over the spacers 150 of tungsten material. A metal layer 320 (e.g., aluminum) is then deposited over the second titanium/titanium nitride (Ti/TiN) liner 310. The result of these steps is illustrated in FIG. 3.
Then a metal etch process is applied to etch the metal layer 320. FIG. 4 illustrates the result of applying the metal etch process. The metal layer 320 is etched away. The “stringers” of tungsten material 150 are etched away. The second titanium/titanium nitride (Ti/TiN) liner 310 is also etched away. Except for the “stringers” 140 that remain on ridges of the dielectric material 110 (as shown in FIG. 4) the first titanium/titanium nitride (Ti/TiN) liner 140 is also etched away.
Then a titanium tungsten (TiW) etch process is applied to etch away the TFR protection material 130 over the thin film resistor (TFR) material 120. The result is shown in FIG. 5. The “stringers” 140 of the first titanium/titanium nitride (Ti/TiN) liner 140 shown in FIG. 4 also remain in FIG. 5.
FIG. 6 illustrates a plan view of the prior art semiconductor device shown in FIG. 5. A first end of the thin film resistor (TFR) material 120 is connected to a first metal contact pad 610. A second end of the thin film resistor (TFR) material 120 is connected to a second metal contact pad 620. The ends of the “stringers” 140 are also connected to first metal contact pad 610 and to second metal contact pad 620. The problem is that the titanium/titanium nitride “stringers” 140 electrically short the thin film resistor (TFR) material 120 between the metal contact pads, 610 and 620.
Therefore, there is a need in the art for a system and method that is capable of patterning a thin film resistor in a manner that does not create the problems inherent in prior art methods. In particular there is a need in the art for a system and method for patterning a thin film resistor that is immune to the effects of topography on the critical dimensions (CDs) of the thin film resistor. SUMMARY OF THE INVENTION
To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide an efficient system and method for manufacturing a thin film resistor.
In one advantageous embodiment of the present invention a trench is etched in a layer of dielectric material. Then a thin film resistor layer is deposited so that the thin film resistor layer lines the trench that has been etched in the layer of dielectric material. Then a thin film resistor protection layer is deposited to fill the trench.
Then a chemical mechanical polishing process is applied to remove the excess portions of the thin film resistor layer and to remove the excess portions of the thin film resistor protection layer. Then an interconnect metal is deposited and patterned to create an opening over the thin film protection layer in the trench. Then a central portion of the thin film resistor protection layer is removed down to the thin film resistor layer that is located at the bottom of the trench.
The resulting thin film resistor structure is immune to the effects of topography on the critical dimensions (CDs) of the thin film resistor. In addition, the resulting thin film resistor structure does not create metal “stringers” that can electrically short out the thin film resistor.
It is an object of the present invention to provide an efficient system and method for manufacturing a thin film resistor.
It is also an object of the present invention to provide a system and method for manufacturing a thin film resistor to eliminate the effects of topography on the critical dimensions (CDs) of the thin film resistor.
It is yet another object of the present invention to provide a system and method for manufacturing a thin film resistor in which metal “stringers” are eliminated from the structures associated with the thin film resistor.
It is still another object of the present invention to provide a system and method for manufacturing a thin film resistor in which a chemical mechanical polishing process is used instead of a mask and etch process.
The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.
Before undertaking the Detailed Description of the Invention below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like; and the term “controller” means any device, system or part thereof that controls at least one operation, such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as future uses, of such defined words and phrases.